Ubuntu 12.04 Codename Precise Pangolin which has been scheduled to be released today (April 26th 2012) has been released just now , See the changes and improvement here until wait official review from Ubuntu.Buzz! soon.

Upgrade to Ubuntu 12.04 (Ubuntu 11.10/10.04 LTS)
To upgrade Ubuntu 11.10 or Ubuntu 10.04 LTS to Ubuntu 12.04 you can press press Alt+F2 then type "update-manager -d" (without the quotes) into the command box that appear. Update Manager should open up and tell you the new distribution is available. Click Upgrade and follow the on-screen instructions.

Download Ubuntu 12.04 LTS
Download Ubuntu 12.04 LTS Precise Pangolin Image trough following link, A full list of available release also available in BitTorrent files :